when has a 13.5 hp motor been lower than 28ci?? 12hp flattys and 12 hp ohv's are 28's. 14hp ohv's are 28's,11hp flattys are 25ci.......why would a 13.5 be smaller???? does not make sense to me! check numbers on valve cover as said before.

when has a 13.5 hp motor been lower than 28ci?? 12hp flattys and 12 hp ohv's are 28's. 14hp ohv's are 28's,11hp flattys are 25ci.......why would a 13.5 be smaller???? does not make sense to me! check numbers on valve cover as said before.

There is a newer motor that is 21 CI OHV..... they are 12.5-13.5 HP.Short deck, short stroke, 28 piston bore.

I think the smallest hp rated 21 cube motor is 10.5 hp. Hence them being allowed in AP.

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You never win a race by focusing on one aspect of the race! Motor isn't everything, but you better have a good one! Chassis too! But remember, a driver can take a slow machine and make it faster! I may not have/be the best of any of these but I'm trying!Chris Cox- CP/Mod X, AP2016 ALL AMERICAN CP/Mod X Champion2015 USLMRA AP Champion2014 USLMRA AP Runner Up2013 USLMRA AP Champion2012 SRUSAAO ModX/CP Champion2012 USLMRA CP Champion2012 US Open AP Champion 2011 SRUSAAO MOD-X/CP Champion2011 USLMRA FX Points Runner up2011 GALMRA CP Points Champion

I recall this subject being talked about before on here and what i got out of it is that HP rating mean nothing. Isnt that why briggs got sued and is moving to the cc ratings and not using hp? its the cubic inches/cc's that matter.

I havent seen a 13.5 in person so i am only assuming they are the same. But i know for a fact that the 10.5 ohv and the 12.5 ohv are the same thing, or have the same cubic inches and block anyways...